A successful HIV-1 vaccine will likely have to induce strong CD4 and CD8 T cell immunity. For example, there is evidence that CD4+ T cells are required for the function of virus-specific CD8+ T cells in many experimental models of immunity, and that CD8+ T cells provide resistance against SIV and HIV-1. Likewise, EBV-associated lymphoproliferative disorders develop in AIDS, suggesting a need for CD4+ T cells in resistance in EBV as well. Dendritic cells [DCs) are specialized antigen presenting cells for initial combined CD4+ and CD8+ T cell immunity. Therefore our hypothesis is that the targeting of HIV-1 and EBV antigens to mature, immunostimulatory DCs will lead to strong virus-specific immunity. In the two years of this grant, we have learned to deliver HIV-1 and EBV antigens to DCs with different viral vectors, and we find that these DCs then stimulate strong T cell responses. In other grants, we have injected antigen-bearing DCs to healthy volunteers and elicited rapid and broad T cell immunity in situ. We will now pursue the data along 3 lines: 1] To optimize the use of DCs infected with a non- perturbing, envelope-pseudotyped HIV-1--to elicit strong immunity in culture. This approach will then be used to detect and quantify CD4 and CD8 immune status in important cohorts, 3e.g., exposed uninfected individuals, long term non-progressors, and patients receiving highly active anti-retroviral therapy; 2] To vaccinate, in collaboration with the Walter Reed Army Research Institute vaccine group, volunteers with autologous DCs charged with recombinant avipox. The immunity will then be compared to separate cohorts vaccinated with recombinant avipox directly; an approach that to date has not induced strong or reliable immunity. 3] To use DCs to elicit immunity to Epstein Barr Virus, especially CD4+ T cells specific to EBNA-1. We have identified strong CD4+ T cell responses to the critical EBNA-1 protein and now will use DCs to understand the processing of EBNA-1 and the biological functions of the reactive T cells.